Cold war tensions were underpinned by the fear of nuclear war nuclear weapons derive their energy from nuclear reactions called fission or fusion they are capable of enormous destructive power thousands of times greater than conventional explosives the detonation of some nuclear weapons is capable of destroying an entire city. October 3 1952 the united kingdoms first nuclear test november 1 1952 the us tests the first hydrogen bomb the united states detonated ivy mike the worlds first hydrogen bomb hydrogen bombs or h bombs are many times more powerful than the atomic bombs dropped on hiroshima and nagasaki 1952. The role that the invention of nuclear weapons played in bringing world war ii to an end remains debatable but the fact is undeniable that these powerful new weapons drastically changed the nature and potential intensity of modern warfare thankfully as of january 2014 no nuclear weapons have been employed in combat since august 1945. The atomic bomb and the origins of the cold war the nuclear age began before the cold war during world war ii three countries decided to build the atomic bomb britain the united states and the soviet union britain put its own work aside and joined the manhattan project as a junior partner in 1943